The glyph-orientation-horizontal and glyph-orientation-vertical
properties were originally intended to allow control the orientation of
mixed layout (horizontal and vertical) text. At least
glyph-orientation-horizontal seems to be implemented in WebKit and Opera
(although with somewhat different results[1]), but it isn't in Gecko.
css3-writing-modes solves this by defining the 'text-orientation' property:
http://dev.w3.org/csswg/css3-writing-modes/#text-orientation0
so I suspect we should use that. It has a value "use-glyph-orientation"
which means to use the value of the SVG
glyph-orientation-{horizontal,vertical} properties to determine the
orientation of glyphs. This value has been marked deprecated and at
risk of being removed.
Would it be safe to remove these two properties and just use
text-orientation going forward?
[1] http://people.mozilla.org/~cmccormack/tests/glyph-orientation.svg